Bypassing Gatekeeper Safely in Mac OS X 10.8 Mountain Lion to Run Unverified Software

Mac OS X 10.8 Mountain Lion comes pre-loaded with software called ‘Gatekeeper’, which is designed to help keep malicious software off of your Mac by giving you more control over what you install.  How it works is quite simple – Gatekeeper will either allow you to run:

  1. Only applications downloaded from the Mac App Store
  2. Applications downloaded from the Mac App Store and from identified developers
  3. Any downloaded application.

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These options can be found in System Preferences > Security & Privacy > ‘General’ Tab

By default, Gatekeeper is set to ‘Mac App Store and identified developers.’  This means that a Mac running Mountain Lion will only run applications you have downloaded from the App Store or applications that have been signed with an official Apple Developer ID.  This helps to prevent malware from infecting your computer, as it makes it harder for malicious software posing as real applications to be installed by the user.

Note that Gatekeeper only applies to applications downloaded from the internet – any applications already on your computer or transferred to your computer in another way (i.e. USB, etc.) will not be stopped by Gatekeeper, so be cautious in this regard.

Bypassing Gatekeeper

If you need to install a downloaded piece of software that isn’t signed by an official Apple developer, Gatekeeper will, by default, not allow you to run it. However, there are several simple ways to bypass this security feature and install the application. Note: these methods may require administrative privileges.

  1. The simplest and easiest way is to control-click (or right-click) the downloaded app to run/install, and on the revealed context menu, choose ‘Open.’ On the ensuing dialogue box, choose ‘Open’ as well. Note that this will exempt this file from Gatekeeper, so, if needed, it can be run again by double-clicking. This is the recommended method.

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2. For experienced users:  You can run the terminal command: % xattr -d com.apple.quarantine YourApp.app

3. This is the least safe method, and is not normally recommended.  All downloaded apps will no longer be stopped or checked for authenticity by Gatekeeper.  Choose ‘Anywhere’ on the Gatekeeper   settings.  This will allow you to run any downloaded piece of software (but will still warn you that you are opening a potentially unsafe program).

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Note that if you choose to set Gatekeeper to ‘Anywhere’, you may at any time change this back to a stricter and thus safer setting.  So, you can use the ‘Anywhere’ setting to install needed software (that is unverified by Apple), and change it back to ‘Mac App Store and identified developers’ when finished.

Remember, when installing any piece of software, make sure you know exactly what it is and where it came from.  Gatekeeper is NOT an anti-virus program. If you bypass Gatekeeper on a malicious download, it will infect your computer.  So, always exercise caution when running any new application.

For a more detailed guide about Gatekeeper, visit http://support.apple.com/kb/HT5290

SOURCES:

http://arstechnica.com/apple/2012/07/os-x-10-8/15/#game-of-gates

http://www.apple.com/osx/whats-new/features.html#gatekeeper

http://support.apple.com/kb/HT5290

http://support.apple.com/kb/PH11437

http://knowledge.timespace.com/index.php/article/what-is-the-gatekeeper-feature-on-os-x-108-mountain-lio

http://support.apple.com/kb/PH11432

 

Version 1.0 – 8/03/12 – Written By Alex Wong, BU InfoSec